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COPI – TRAPPII activates Rab18 and regulates its lipid droplet association
Author(s) -
Li Chunman,
Luo Xiaomin,
Zhao Shan,
Siu Gavin KY,
Liang Yongheng,
Chan Hsiao Chang,
Satoh Ayano,
Yu Sidney SB
Publication year - 2016
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.15252/embj.201694866
Subject(s) - copi , microbiology and biotechnology , biology , golgi apparatus , guanine nucleotide exchange factor , lipid microdomain , lipid droplet , adp ribosylation factor , secretory pathway , gtpase , biochemistry , endoplasmic reticulum , membrane
The transport protein particle ( TRAPP ) was initially identified as a vesicle tethering factor in yeast and as a guanine nucleotide exchange factor ( GEF ) for Ypt1/Rab1. In mammals, structures and functions of various TRAPP complexes are beginning to be understood. We found that mammalian TRAPPII was a GEF for both Rab18 and Rab1. Inactivation of TRAPPII ‐specific subunits by various methods including si RNA depletion and CRISPR –Cas9‐mediated deletion reduced lipolysis and resulted in aberrantly large lipid droplets. Recruitment of Rab18 onto lipid droplet ( LD ) surface was defective in TRAPPII ‐deleted cells, but the localization of Rab1 on Golgi was not affected. COPI regulates LD homeostasis. We found that the previously documented interaction between TRAPPII and COPI was also required for the recruitment of Rab18 to the LD . We hypothesize that the interaction between COPI and TRAPPII helps bring TRAPPII onto LD surface, and TRAPPII , in turn, activates Rab18 and recruits it on the LD surface to facilitate its functions in LD homeostasis.